Discussion on paper: Interesting features of a coal dump-ash dam at Kilbarchan Colliery by A. A.B. Williams & P. Maree

Mr Chairman, there are perhaps two aspects which may not have received sufficient emphasis in the paper. The first concerns the pore pressure conditions within the ash dam. It is most significant that, even with increasing height of the ash dam, the water level in some standpipes was still 20 m or more below the surface. The lateral flow through the permeable discard wall may thus be adequate to dispose of all excess water above the actual surface of the sedimented ash. Thus, while a free water surface may be visible, this is not necessarily indicative of hydraulic continuity in the vertical direction.